Configuring NAT Rules

Maps one IP address or network to another IP address or network
in an unregulated round-robin process.

rdr

Redirects packets from one IP address and port pair to another
IP address and port pair.

bimap

Establishes a bidirectional NAT between an external IP address
and an internal IP address.

map-block

Establishes static IP address-based translation. This command
is based on an algorithm that forces addresses to be translated into a destination
range.

Following the command, the next word is the interface name,
such as hme0.

Next, you can choose from a variety of parameters, which determine
the NAT configuration. Some of the parameters include:

ipmask

Designates the network mask.

dstipmask

Designates the address that ipmask is translated
to.

mapport

Designates tcp, udp,
or tcp/udp protocols, along with a range of port numbers.

The following example illustrates how to put together the NAT rule syntax
together to create a NAT rule. To rewrite a packet that goes out on the de0 device with a source address of 192.168.1.0/24 and
to externally show its source address as 10.1.0.0/16, you
would include the following rule in the NAT rule set:

map de0 192.168.1.0/24 -> 10.1.0.0/16

For the complete grammar and syntax used to write NAT rules, see the ipnat(4) man page.